#include<stdio.h>
struct bitree
{
	int val;
	bitree*right;
	bitree*left;
};
void pretree(bitree *T)
{
	if(T==NULL)
      printf("empty");
    else
    {
     printf("%d ",T->val);
     pretree(T->right);
     pretree(T->left);
    }
 } 
int main()
{


printf("");
return 0;
}

